We normally associate echoes with sound, but other waves echo too. For example, radar is based on radio wave echoes.

Light from supernovae moves out in all directions and bounces off dust in the surrounding area. A map of the dust in M82, 11.4 million light years away, was created by measuring how long it took for these light echoes to reach Earth.

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Normally, light echoes are viewed using historical images, but Crotts has used the Hubble Space Telescope to watch them as they appear in the sky.

“You have this really detailed 3D map, all the way over in some distant galaxy where there is really no other way to make such a map,” he says.

It can be difficult to see light echoes because most supernovae are far away, but 2014J is the second-closest ever, after the 1987 supernova in the Large Magellanic Cloud. “It was always expected that M82 would be a good target for searching for light echoes,” says Stephen Fossey of University College London, who first spotted the supernova. “This kind of work is certainly important for probing the dust environment.”

This article appeared in print under the headline “Stellar explosion captures cosmic map of Cigar Galaxy”